1. Field of the Invention
The present invention relates to a color image forming apparatus for developing latent images with a plurality of developing units.
2. Description of the Prior Art
The color image forming apparatus is generally equipped, with a plurality of developing units for multicolor developments, and with three developing devices which are charged with red, blue and black toners, respectively, to sequentially develop the latent images, which are formed on a photosensitive drum in response to signals of the respective colors, by applying high-frequency bias voltages thereby to form a color toner image on the photosensitive drum by composing those developed images.
For the aforementioned development by applying the high-frequency bias voltages, each of those developing devices is required to have its built-in developing sleeve positioned at a spacing of as small as 0.4 to 0.5 mm from the circumferential surface of the photosensitive drum and adjusted with a precision of a unit of 0.01 mm and to be freely attached to and detached from the body of the image forming apparatus for toner supplying or cleaning and inspecting operations although it is positioned so close to the photosensitive drum.
In order to satisfy these requirements, however, each of the developing devices has to be mounted on the corresponding mounting portion of the image forming apparatus body through a remarkably high precision fitting device. Adoption of this construction will undesirably deteriorate the commercial value of the image forming apparatus because it enlarges the scale of the construction of the apparatus to raise the production cost and to degrade the operability of mounting and demounting the developing devices.